Up until now, many methods of hindering avalanches have been used, but with rather bad results, though. Racks and cones have been raised, ditches and defense walls (embankments) have been built, but these protection systems have not been completely effective: Racks have (been swept away, avalanches have floated over the cones; embankments and ditches require a lot of land and can be dangerous. Embankments are also still at an experimental stage. Estimates show that the first avalanche to fall on a defense wall will almost fill up the slope in front of the wall putting at risk the village or town, that the wall is supposed to protect in the event of a secondary avalanche falling over the first one. In addition, the building of a defense wall or ditches can greatly damage the land, not to mention the view. Building a defense wall is also costly and time-consuming.